The present invention relates to medical instruments, and more particularly, to a disposable cover or sheath for the probe of a clinical thermometer.
The diagnosis and treatment of many body ailments depends upon an accurate reading of the internal or core temperature of a patient's body, and in some instances, upon a comparison to a previous body temperature reading. For many years, the most common way of taking a patient's temperature involved the utilization of a Mercury thermometer. This approach has a number of drawbacks. First of all, such thermometers are normally made of glass. They must be inserted and maintained in the patient's mouth or rectum for several minutes. This is often discomforting to the patient. Furthermore, such thermometers can break, resulting in serious lacerations or Mercury poisoning. In addition, Mercury thermometers are difficult to read, must be sterilized, and must be "shaken down" vigorously to place the Mercury at the bottom end prior to use.
Because of the above drawbacks of conventional Mercury thermometers, electronic thermometers were developed and are now in widespread use. Typically, the commercialized versions of such electronic thermometers have been designed for taking a patient's temperature orally or rectally. They have a probe connected by wires to a remote unit containing an electronic circuit. The probe is inserted into a protective, disposable plastic cover or sheath before being inserted into the patient's mouth or rectum. After the patient's temperature is taken, the sheath is discarded, and the probe is inserted into another sanitary sheath for taking the next patient's temperature. In this manner, the electronic thermometer is rapidly reusable without communicating infectious organisms between patients.
The foregoing type of electronic thermometer typically uses predictive techniques, by which the patient's temperature reading is taken in a significantly shorter time period, for example thirty seconds, compared to the several minutes required for the conventional Mercury thermometers. Such electronic thermometers normally have meters or other displays which enable the operator to determine the temperature much more readily than reading the position of the terminal end of a column of Mercury inside a glass tube. The probe is typically an elongated rod of small diameter. The sheath comprises a hollow tube having an open end and a closed, somewhat pointed end. It has a round cross-section of relatively small diameter and is made of a plastic material which is not toxic.
The tympanic membrane is generally considered by the medical community to be superior to oral, rectal or auxillary sites for taking a patient's temperature. This is because the tympanic membrane is more representative of the body's internal or core temperature and more responsive to changes in core temperature. Heretofore, efforts to provide a method and apparatus for measuring the body temperature via the external ear canal have not been successful. One approach has been to use a thermister, thermocouple or some other type of device requiring physical contact with the tympanic membrane. This approach is undesirable because of the discomfort to the patient and the danger of physical injury to the tympanic membrane. Another approach has directed air against the tympanic membrane and attempted to measure the increase in temperature in returning air in order to derive the patient's temperature. Clearly this approach has significant drawbacks in regard to accuracy. A third and better approach to tympanic temperature measurement involves sensing infrared emissions in the external ear canal. In order to accomplish this efficiently, a probe must be partially inserted into the external ear canal. A cover or sheath must be provided for enclosing the frontal portion of the probe to present a clean, sanitary surface to the patient and also to keep the probe free of ear wax and hair. The probe cover or sheath must be made of material which is substantially transparent to infrared radiation.
As used herein, the term "speculum" shall include any type of cover or sheath adapted to fit over a probe for the purpose just described. Preferably, such a speculum is inexpensive so that it can be disposed after a temperature reading has been taken and a new speculum installed over the probe for the next patient. This eliminates any need to sterilize such speculums.
U.S. Pat. No. 3,282,106 of Barnes suggests the concept of an infrared thermometer that may be placed in the ear cavity to measure body temperature. An infrared detector receives radiation through an internally polished truncated cone which acts as a shield and which is partially inserted into the ear canal. This cone is apparently a permanent part of the apparatus and is not removable or disposable. The specification of the Barnes patent indicates that this cone was not intended to actually touch any portion of the outer ear. However, Barnes indicates that the cone may lightly touch portions of the outer ear because of lack of skill of the operator. Nevertheless, no protective speculum for the cone is disclosed in Barnes. The aforementioned Barnes patent also discloses an alternate embodiment including a conventionally shaped ear plug which contacts the external ear canal but is not provided with a speculum.
U.S. Pat. No. 3,581,570 of Wortz discloses a tympanic temperature sensing device which has positioning means to establish a fixed relationship between the eardrum and a radiometer. A polyethylene shield fits over the probe portion to protect the radiometer. It does not appear that the shield is readily replaceable. Furthermore, the shield appears to be a cup-shaped member of uniform thickness. The very small width and length of the cup-shaped shield would make it very difficult to handle, install and replace.
U.S. Pat. No. 3,878,836 of Twentier discloses a disposable speculum for an infrared sensing tympanic thermometer. This speculum has the general shape of a funnel and has open forward and rearward ends. The patent indicates that preferably the speculum is formed of polyethylene. The principal drawback of this speculum is that its open forward end which is partially inserted into the ear canal may become clogged with wax or other debris and impair proper functioning. Also, the open forward end will permit germs and other foreign matter to be transferred to the thermometer instrument itself, thus presenting a risk of contamination and spreading of bacteria and viruses between patients.
A proposed ASTM standard for probe covers for body temperature thermometers refers to a minimum rupture pressure of 1.2 PSI. No specific construction for a probe cover is described in the ASTM standard.